The present invention relates to an auxiliary jig used for forming a structure made of a fiber-reinforced composite.
Stiffened panels made of a fiber-reinforced composite (prepreg) are light in weight and high in strength to have been widely used for automobiles, ships, aircrafts, etc. The stiffened panels generally comprise a skin strengthened by a plurality of stiffeners (stringers and frames), the skin and the stiffeners being integrally formed. FIG. 1 is a partial perspective view showing an example of the stiffened panel. A stiffened panel 1 shown in FIG. 1 comprises a skin 2 and a stiffener 3 integrally formed therewith. As shown in FIGS. 4(a) and 4(b), the stiffened panel may be produced by a method comprising the steps of: placing a skin member 2 and a preformed stiffener member 31 each made of a fiber-reinforced composite on a forming tool 4; disposing a couple of jigs 5a and 5b on the preformed stiffener member 31; and integrally forming the skin member 2 and the preformed stiffener member 31 by heating under a pressure using a pressure bag, etc.
The above-mentioned method is disadvantageous in that a resin contained in the fiber-reinforced composite often flows out from an interspace between the jigs 5a and 5b in the direction of arrow A shown in FIG. 4(b) while heating under a pressure. If a large quantity of the resin flows out from the interspace, the resultant fiber-reinforced composite structure is poor in such a quality as strength, rigidity, etc. Thus, as shown in FIG. 5, the resin has been conventionally restrained from flowing out by sticking a temperature resistant tape 7 to the preformed stiffener member 31 and the jigs 5a and 5b disposed thereon. However, the process of sticking the temperature resistant tape is complicated and troublesome, thereby requiring much effort.
Further, in the above-mentioned method, the jigs 5a and 5b often fall down while heating under a pressure as shown in FIG. 6. In this case, the resultant fiber-reinforced composite structure is poor in form accuracy with unevenness stiffener thickness. The fiber-reinforced composite structure can be formed with high form accuracy by using a large-scale jig together with the jigs 5a and 5b, however, this results in increased costs and poor workability.
An object of the present invention is to provide an auxiliary jig used for forming a structure made of a fiber-reinforced composite with high form accuracy without reduction of strength and rigidity.
As a result of intensive research in view of the above object, the inventors have found that a structure made of a fiber-reinforced composite having desired strength and rigidity can be formed with high form accuracy by using a particular auxiliary jig together with a couple of jigs while forming. The present invention has been accomplished by the finding.
Thus, an auxiliary jig of the present invention is used with a couple of jigs for forming a structure made of a fiber-reinforced composite by heating under a pressure, the auxiliary jig being provided between the couple of jigs to prevent the jigs from falling down and to restrain a resin contained in the fiber-reinforced composite from flowing out from an interspace between the jigs.
The auxiliary jig of the present invention preferably comprises a rigid portion and an elastic portion. The rigid portion is preferably made of a stainless steel, aluminum, graphite or CFRP, and the elastic portion is particularly preferably made of a silicone rubber.
The auxiliary jig of the present invention is particularly preferably used for forming a stiffened panel. Thus, a stiffened panel having uniform, excellent qualities can be produced with high form accuracy by a method comprising the steps of: placing an skin member and a preformed stiffener member each made of a fiber-reinforced composite on a forming tool; disposing the couple of jigs on the preformed stiffener member; providing the auxiliary jig of the present invention between the jigs; and integrally forming the skin member and the preformed stiffener member by heating under a pressure.